Synthesis of Thermally Stable Highly Ordered Nanoporous Tin Oxide Thin Films with a 3D Face-Centered Orthorhombic Nanostructure

Abstract

Thin films of nanoporous tin oxide with a 3D face-centered orthorhombic nanostructure have been synthesized by self-assembly that is controlled by post-coating thermal treatment under controlled humidity. In contrast to the conventional evaporation-induced self-assembly (EISA), the films here have no ordered nanostructure after dip-coating. However, the initial coatings are formed under conditions that inhibit significant hydrolysis and condensation for extended periods. This allows the use of postsynthesis thermal vapor treatments to completely control the formation of the nanostructure. With EO106-PO70-EO106 (Pluronic F127) triblock copolymer as the template, highly ordered nanostructures were generated by exposing the disordered films to a stream of water vapor at elevated temperature, which rehydrates the films and allows the formation of the thermodynamically favored phase. Further exposure to water vapor drives the condensation reaction through the elimination of HCl. The X-ray diffraction pattern from the nanostructure was indexed in the space group Fmmm as determined by analysis of 2D small-angle X-ray scattering patterns at various angles of incidence. The nanostructure is then stabilized and made nanoporous by extended controlled thermal treatments. After self-assembly and template removal, the films are thermally stable up to 600 degrees C and retain an ordered, face-centered orthorhombic nanostructure.

Engineering metal oxide nanostructures for the fiber optic sensor platform

“…In the wet chemical synthesis of the precursor, Pluronic F-127, a triblock copolymer was used as the structure direct agent for the nano-engineering of SnO 2 [15,[36][37][38]. By controlling its mole fraction, the porosity of the SnO 2 is controlled on the tens-of-nanometers scale to tailor the refractive index of the nano-material.…”

Generation of Self‐Assembled 3D Mesostructured SnO2 Thin Films with Highly Crystalline Frameworks

“…Tolbert and coworkers, [18] Urade and Hillhouse, [7] and Grosso et al [11a] had already pointed out that a careful and well-chosen temperature program is needed to avoid mesostructural collapse during thermal treatment of Pluronic F127-derived SnO 2 and TiO 2 mesoporous films. These difficulties in the preparation of SnO 2 films could now be overcome by the superior templating properties of an appropriate structure-directing agent.…”

“…[6] The most significant progress was recently achieved by Urade and Hillhouse, [7] who demonstrated that SnO 2 films with high mesopore regularity can be obtained by using Pluronic templates. This procedure involved a complex Crack-free, mesoporous SnO 2 films with highly crystalline pore walls are obtained by evaporation-induced self-assembly using a novel amphiphilic block-copolymer template ("KLE" type, poly(ethylene-co-butylene)-block-poly(ethylene oxide)), which leads to well-defined arrays of contracted spherical mesopores by suitable heat-treatment procedures.…”

Nanoarchitectonics for Mesoporous Materials

“…Hillhouse et al successfully removed the surfactants from mesostructured tin oxide films prepared through the water-vapor treatment. 451 By careful thermal treatment, consisting of heating at temperatures ranging from 50 to 250°C with a 30°C step and a 12 h pause at each temperature, a highly ordered mesoporous tin oxide film with a 3D face-centered orthorhombic nanostructure was obtained.…”